In digital power circuits, since control is performed based on digital values, it is necessary to perform A/D conversion using an A/D converter to convert an analog value such as an output voltage or the like of a DC/DC converter necessary for control to a digital value and to input the digital value to a control circuit. However, in switching power circuits, since a large amount of noise occurs with switching of a DC/DC converter and affects the operation of an A/D converter, it is difficult to obtain an accurate digital value.